1. Technical Field
The present invention relates to a device for selectively eliminating resilience incorporated within a front end accessory drive belt tensioning system for an automotive engine.
2. Background Information
Front end accessory drives incorporated in modern automotive engines are called upon to power a number of accessories such as an air conditioning compressor, alternator, power steering pump, water pump, air injection pump, and other devices. Problems have arisen with front end accessory drives because certain accessories, such as engine cooling fans or alternators, have considerable rotational inertia. This may cause objectionable belt noise during certain operating modes of the engine. For example, during the one-two upshift of an automatic transmission, the engine will decelerate at an exceedingly rapid rate. As a result, the inertia of the alternator may cause the alternator to actually become a driving portion of the system instead of the engine's crankshaft during the wide-open throttle upshift. This overdrive condition caused by inertia of the alternator or engine driven cooling fan, may cause a slack portion or "bubble" to develop in the accessory drive belt, thereby causing a squeal. Unfortunately, motorists may incorrectly identify the squeal with defective parts and as a result seek expensive albeit unneeded warranty repairs.
In particularly severe cases, the bubble phenomenon may result in the belt jumping off one of more of the pulleys, and this may lead to a very expensive repair, without remedying anything. A tensioner according to the present invention avoids the problem of undesirable slack developing in a drive belt with a simple mechanical device divorced from the engine control system.